This study examined information processing of line-drawn picture categorizing by preschool (5 and 6-year-olds) children, using a Stroop-like picture-auditory categorizing task. In this task, participants were required to respond category of the target pictures (animal or fruit) ignoring the distracting pictures. To clarify the effect of semantic relations on the amount of interference, the following conditions were presented under the combination of target and distracting pictures: same stimulus (SS), same category (SC), different category (DC), neutral (N), and control (C). To investigate the time course of processing, stimulus onset asynchrony (SOA) between target and distractor was varied. In the results, Stroop-like interference effect was seen in children, contrastively, no interference effect was seen in adults. On the semantic interference, difference from picture naming task (e.g. Tazume, 1997), the RT of DC condition was longer than that of SC condition (reversed semantic interference). These results was discussed in terms of processing related to semantic memory.